'Good pace', but Rossi puzzled by fast-lap fade

Yamaha team-mate Valentino Rossi and Maverick Vinales were the only riders in the top 13 not to lap faster on the final day at the Sepang MotoGP test.

Rossi said it replicated their experiences on the 2016 bike at Valencia in November, although he took comfort from the fact that his pace on used tyres was 'very good'.

"We are a little bit worried, we need to understand why, because in the Valencia Test after the last race it happened exactly the same," said Rossi, speaking in the Sepang paddock.

"On the Tuesday [at Valencia] me and also Maverick had a good feeling with the bike and tyres. Next day, same bike, same tyres, same temperature we lose 3-4 tenths and we don't understand why."

Vinales and Rossi had been first and second on day two in Malaysia, but dropped to 18th and eighth respectively by the end of the final day.

"Today it happened a little bit the same [as Valencia], so we need to understand why.

"We were struggling a little bit more from the morning with the grip. It was a bit more difficult to ride the bike at the limit."

That fast-lap puzzle was the only real damper on an otherwise highly positive test for the Italian, who is returning to his favoured 2016 chassis, which Vinales and Tech 3's Johann Zarco will also use this season.

"In the end for the fastest lap I'm not so far - the position is not fantastic - but my pace is very good," said Rossi, who rode with a replica of his 1997 helmet on day two of the test (pictured).

"Today we worked a lot, we finish our programme because we had a lot of stuff. For me the biggest improvement is my feeling with the bike, because I feel comfortable, and also the pace: Compared to last year I've improved a lot because last year I suffered more with the degradation of the tyre."

Rossi has several "small modifications" of the 2016 chassis to try as Yamaha aims to retain the feeling of the original design, but with better end-of-race tyre life.

"Usually weight distribution and stiffness," replied Rossi, when asked about the difference between the 2016 chassis he has available.

"We had a lot of stuff to try here and at the end it was a good test. We worked hard.

"Yesterday night I was optimistic to improve the lap time. But was it impossible. Was a bit more difficult, especially with the new tyre. Because with the used tyre my pace was good.

"So we need to understand why."